Filter systems and filter elements that are used to filter a fluid such as fuel are well-known in all fields that use combustion engines including earthmoving, construction and mining equipment. A filter system is often provided that separates water or contaminants from the fuel before it enters the engine. A filter element is often provided as part of this system that includes a filter media wrapped around a center tube. The configuration of the tube and the filter media is often substantially circular or cylindrical.
For example, FIG. 1, illustrates a filter system 100 having a base 102, a canister 104, and a filter element 106. The general construction and use of a canister filter system is understood by those of ordinary skill in this art. Thus, all the details of the construction and use of canister filter system 100 need not be explained here. The canister filter system 100 may be used to filter fluids such as diesel or gasoline or other liquid fuels, lubrication oil, hydraulic fluid for hydraulic power systems, transmission fluid, or even possibly intake air for an engine. The canister filter system 100 may also be used as a fuel/water separator filter. The canister filter system 100 with the features described herein could be adapted by those of ordinary skill in this art to serve many different purposes and suit many other applications.
The base 102 includes an inlet channel 108 for fluid inlet into the filter system 100, and an outlet channel 110 for fluid outlet from the filter system 100. The base 102 also includes base threads 112. Other attachment structure than threads may be used.
The canister 104 includes an open end 114 and a closed end 116. Adjacent the open end 114 are canister threads 118 which can be engaged with base threads 112 to hold the canister 104 to base 102. Threads are one example of engagement structures which may be included on the base 102 and canister 104 to form a releasable engagement. Other engagement structures may be used as will be recognized by those of ordinary skill in this art.
The filter element 106 may take many different forms to suit a particular application. In the illustrated embodiment, the filter element 106 is well suited for filtering fuel or lubrication oil. The filter element 106 may include annularly arranged filter media 120 circumferentially surrounding a central reservoir defined by center tube 122. Axial ends of filter media 120 are sealed by end plates or caps. Open end cap 124 defines an axial open end of filter element 106. The open end cap 124 is termed “open” because it includes an opening 126 for allowing passage of fluid to outlet channel 110 from the central reservoir defined by center tube 122. Closed end cap 128 defines an axial closed end of filter element 106 at its bottom portion. The closed end cap 128 is termed “closed” because it prevents any fluid outside the filter element 106 adjacent an axial end of filter media 120 from flowing unfiltered into center tube 122. Open end cap 124 and closed end cap 128 may each be joined to the center tube 122 via welding, adhesives, etc. Alternatively, several or all of center tube 122, open end cap 124, and closed end cap 128 may be constructed as unitary components. Alternatively, they may be constructed from multiple components. The top cap may be closed and the bottom cap may be open in other embodiments.
Fluid (denoted by arrows 134) to be filtered enters from the inlet channel 108 and flows to the annular cavity 130 between canister 104 and the filter media 120. The fluid then passes into and through filter media 120, then into center tube 122 through the perforations 132 shown therein in FIG. 1. The fluid exits the center tube 122 through the open end cap 124 and the opening 126 into the outlet channel 110. The open end cap 124 and closed end cap 128 help define the fluid channels into and out of filter media 120, preventing any fluid from flowing directly to the outlet channel 110 and bypassing filter media 120.
First and second annular seals 136 and 138 may advantageously be included on filter element 106 and also help define and seal fluid passageways into and out of filter element 106. First annular seal 136 may be included on the open end cap 124 around the opening 126 and adjacent the axial open end of filter element 106 to help seal the inlet channel 108 from the outlet channel 110. Second annular seal 138, larger in diameter than first annular seal 136, may be formed circumferentially around the open end cap 124 to provide the seal between canister 104 and base 102, or in other words provides a seal to prevent fluid in inlet channel 108 from leaking out of the joint between canister 104 and base 102. First and second annular seals 136, 138 may be integrally formed with open end cap 124, or attached with adhesives or other methods, as is known in this art. When first and second annular seals 136, 138 are integrally formed on or included on open end cap 124, proper replacement of these seals is assured when the filter element is replaced at proper intervals. Otherwise, a technician may fail to properly replace the seals at appropriate intervals, which could result in leakage out of the system, or leakage within the system allowing unfiltered fluid to bypass the filter element 106 and lead to contamination.
A drain 140 is typically disposed at the bottom of the filter housing and opened via some type of threaded connection. However, the filter assembly and filter line connected to the filter assembly is generally otherwise a closed system. Without a vent to replace outgoing fluid and contaminants with air, the contaminants either do not flow out of the housing or, if they do, they exit the drain inefficiently in spurts. A drain reservoir 142 is provided at the bottom of the canister 104 that allows water or other contaminants to settle there over time. Eventually, these substances are drained from the reservoir via the drain 140. Any drain known or that will be devised in the art may be used for any of the embodiments discussed herein.
The filter element 106 may have a generally cylindrical configuration that defines a longitudinal axis L and a radial direction R. Other configurations are possible. Before attaching a filter element 106 to a filter system 100, the filter element 106 is typically primed by pouring some of the fluid such as fuel into the filter element 106. A fill guard 144 is shown provided in FIG. 1 to help prevent unfiltered fluid from entering the center tube 122, which could allow the fluid to enter the engine unfiltered after the filter element 106 has been attached to the filter system 100. Since there is no standpipe, air may enter penetrate the filter media exit filter before any the desired fluid such as fuel has had a chance to get through the filter media. This air bubble may reach a pump or the engine, causing problems starting the engine.
FIG. 2 shows another design of a center tube 122′ with a standpipe 146. The standpipe eliminates the problem of poor startup caused by air bubbles as the bubble of air will get trapped near the top of the annular flow passage 148 next to the standpipe 146. A drawback of the design of the center tube 122′ of FIG. 2 is that the bottom of the tube needs to be open as a mold core telescopes from the bottom to form the outer annular flow passage 148. Similarly, another mold core telescopes from the top to form the inner conical flow passage 150 of the standpipe 146 when the center tube 122′ is made using an injection molding process. This limits the versatility of the structures that may be formed at the ends of the center tube and may increase mold complexity and cost beyond what is desirable.